Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$11.43	9.527%	$12.5189	$12.52	$12.50	$12.50
Purchase #2	$249.55	3.636%	$258.6236	$258.62	$258.60	$258.60
Purchase #3	$63.84	11.578%	$71.2314	$71.23	$71.25	$71.20
Purchase #4	$221.90	11.734%	$247.9377	$247.94	$247.95	$247.90
Purchase #5	$161.71	4.836%	$169.5303	$169.53	$169.55	$169.50
Purchase #6	$226.79	12.437%	$254.9959	$255.00	$255.00	$255.00
Purchase #7	$181.32	8.441%	$196.6252	$196.63	$196.65	$196.60
7 purchase totals =	$1,116.54		$1,211.4630	$1,211.47	$1,211.50	$1,211.30